The Korean travelers were removed to separate facilities without prior notice, despite being asymptomatic and traveling from areas other than the banned Daegu and North Gyeongsang Province, the region hit hardest by the coronavirus spread here.

Their passports have been confiscated by Vietnamese authorities, according to local media reports. Ahn Sung-mi reports on The Korea Herald.

“Embassy officials are providing consular support to the people detained in the facilities, and seeking ways to help them,” a senior official at the ministry said on condition of anonymity. “Most of people who are quarantined are residing in Vietnam for education and business purposes, and have not expressed a desire to return to Korea yet. But if they wish to return, we will come up with measures.”

The ministry also called in Vietnam’s top envoy in Korea to lodge a protest over the country’s latest measure, and requested to prevent it from recurring in the future.

Effective Thursday, Vietnam banned the entry of foreign nationals who have traveled to the southeastern city of Daegu and neighboring North Gyeongsang Province, the area that accounts for 87 percent — 3,260 cases — of the total infected number of 3,736 as of Sunday.

For arrivals from other regions in here, Vietnam said they are required to go into self-quarantine for two weeks, but instead, authorities have been transporting Koreans into isolated facilities.

Vietnam also suspended a visa-waiver program for Korean visitors on Saturday.

Separately, an Asiana Airlines flight to Hanoi had to turn back en route after Vietnamese authorities banned it from landing at Hanoi’s Noi Bai Airport.

Asiana Airlines flight 729 departed at 10:10 a.m. on Saturday, but at 10:30 a.m., Vietnamese authorities denied it permission to land, and instead instructed it to land at Van Don International Airport, about 140 kilometers from Hanoi.

Asiana decided to cancel the flight and return to Seoul, as the carrier had no history of using the suggested airport.

Vietnamese authorities also prohibited Korean airliners from using an airport in Ho Chi Minh City, and instead to land at Can Tho International Airport, a four-hour drive away.

Due to ceased flights between Korea and Vietnam, Asiana Airlines and Korean Airlines have been sending empty planes with crew members, known as ferry flights, to Vietnam to bring back Korean passengers, before the country halts all visitors from here.

Vietnam’s stringent move concerns Korea, as it could spread even further to other regions. The measure arrives despite Seoul’s call to refrain from “excessive measures,” with Foreign Minister Kang Kyung-wha calling up her Vietnamese counterpart to retract the move.

As of Sunday, over 78 countries are imposing entry restrictions and special quarantine measures on those traveling from Korea.

For once an airline may have wished it was not on-time.

Asiana Airlines flight 729 departed the gate at Seoul Incheon international airport on schedule at 10:10am on February 29, and a few minutes later took off for the 4.5 hour journey to Hanoi. But at 10:30am, Vietnamese authorities notified Asiana that Korean carriers could no longer land at Hanoi. Will Horton reports on Forbes.

Vietnam gave the option to instead divert to Van Don international airport at Quảng Ninh Province, 140km away from Hanoi, the Korean embassy in Vietnam said. Asiana, which does not normally fly to Van Don, decided to cancel the flight and have it return to Seoul. Flight OZ729 landed back at Incheon about two hours after it took off. The flight reached a maximum altitude of 38,000 feet, according to Flightradar24, and it was nearing Shanghai around the time it turned around.

“We believe it is connected with the spread of the new coronavirus,” an Asiana spokesperson told Yonhap. Korea has the most confirmed cases outside of China. Vietnam this past Tuesday banned the entry of Koreans who had been in the city of Daegu and nearby county of Cheongdo, where the coronavirus outbreak is concentrated.

This was not a total ban on Korean visitors, but travel demand is already significantly weakened, evidenced by the Asiana flight having 40 passengers onboard the A330-300, which seats between 275-298.

While the Asiana flight returned to Seoul, Vietnam Airlines and VietJet had their Seoul-Hanoi flights land in Hanoi as planned. Most other Korea-Vietnam flights are cancelled, especially those from Korea’s low-cost carriers. Korean visitors to Vietnam have rapidly grown, lured by inexpensive resorts closer to Vietnam than traditional getaways further in Southeast Asia, like Thailand and Indonesia.

Korean visitors to Vietnam grew by 23% to 3.1 million in the first nine months of 2019, the latest figures available. Vietnam’s central coastal city of Da Nang is especially popular with Koreans. Before the coronavirus, there were upwards of 20 daily flights between Korea and Da Nang. Vietnam was an important market for Korea’s numerous LCCs, and reflects another key destination seeing a sharp drop in demand. Korea’s LCCs were impacted by last year’s travel downturn to Japan and this year’s coronavirus impacting inbound demand from China.